feat(athena-junior): add athena_council bulk launch tool

- Create src/tools/athena-council/ with council-launcher, tool factory, types
- Launch all council members in parallel via BackgroundManager with writeOutputToFile: true
- Wire tool into registry with backgroundManager + councilConfig dependencies
- Grant athena-junior athena_council permission, remove task permission
- Update non-interactive prompt to use athena_council instead of task tool
- Add explicit stop-after-result instruction to prevent post-output text
- 23 tests (14 tool + 9 launcher) using real temp files, no mock.module

src/plugin/tool-registry.ts

@@ -30,6 +30,7 @@ import {
   createTaskUpdateTool,
   createHashlineEditTool,
   createPrepareCouncilPromptTool,
+  createAthenaCouncilTool,
 } from "../tools"
 import { createCouncilFinalize } from "../tools/council-archive"
 import { getMainSessionID } from "../features/claude-code-session-state"
@@ -282,6 +283,10 @@ export function createToolRegistry(args: {
     ...hashlineToolsRecord,
     prepare_council_prompt: createPrepareCouncilPromptTool(ctx.directory),
     council_finalize: createCouncilFinalize(ctx.directory),
+    athena_council: createAthenaCouncilTool({
+      backgroundManager: managers.backgroundManager,
+      councilConfig: pluginConfig.agents?.athena?.council,
+    }),
   }
 
   for (const toolDefinition of Object.values(allTools)) {